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I don't know if the total electromagnetic radiation in the universe is finite or not.

But either way: what is the origin of the electromagnetic radiation in the universe? Can we say that all of it originated from accelerating charges?

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what is the origin of the electromagnetic radiation in the universe? Can we say that all of it originated from accelerating charges?

The concept of the origin of a photon probably isn't very well defined. E.g., I don't think there's any way to define whether a scattered photon is still the "same" photon.

But in any case, our default expectation is that at arbitrarily short times after the big bang, the conditions of the universe were in some sense statistically likely. This expectation seems to be violated for gravitational waves, but in other respects it seems to be in fairly good agreement with observation. (It can't be 100% true, because then the universe would have started out in a state of thermal equilibrium, and it then couldn't have evolved into its present state without violating the second law of thermodynamics.) For this reason, we expect the universe at its earliest stages to have contained a fairly representative mixture of all the types of particles, in proportions governed roughly by thermodynamic equilibrium. That would have included photons. So in this sense we have strong reasons to expect that photons have existed in our universe that could not have been made by accelerating charges.

However, this is probably not typical of the vast majority of photons we could observe today (subject to the ambiguity of the "origin" of a photon). Up until the universe became transparent to light around 100,000 years after the big bang, photons were being frequently absorbed by matter.

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  • $\begingroup$ Hmm. Could photons exist before electroweak symmetry breaking? $\endgroup$ – PM 2Ring Apr 6 '18 at 17:05
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The question was too board. Notice there were many kind of electromagnetic radiation, with different spectrum and from different time. Until now we had seen from the beginning of universe to nearby starts.

Not all from accelerating charge, i.e. quantum.

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  • $\begingroup$ Please fix your spelling and grammar errors. In its current state your answer is almost incomprehensible. $\endgroup$ – PM 2Ring Apr 6 '18 at 16:59

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